Method, system and apparatus

ABSTRACT

A method comprising transmitting beam cluster information to a user equipment, the beam cluster information defining a plurality of beam clusters and beam identification information for each of a plurality of beams in a respective beam cluster of the plurality of beam clusters; and transmitting, to the user equipment, at least one beam based on the beam cluster information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation patent application of U.S. application Ser. No.16/300,059, filed Nov. 9, 2018, entitled “METHOD, SYSTEM AND APPARATUS”which is a national stage entry of International Application No.PCT/EP2017/061243, filed May 11, 2017, entitled “METHOD, SYSTEM ANDAPPARATUS” which claims the benefit of priority of GB 1608270.3, filedMay 11, 2016, both of which are hereby incorporated by reference intheir entireties.

FIELD

Some embodiments relate to a method, system and apparatus in a scenariowhere beam forming of transmission and/or receiving beams is used.

BACKGROUND

A communication system can be seen as a facility that enablescommunication sessions between two or more entities such as userterminals, base stations/access points and/or other nodes by providingcarriers between the various entities involved in the communicationspath. A communication system can be provided for example by means of acommunication network and one or more compatible communication devices.The communication sessions may comprise, for example, communication ofdata for carrying communications such as voice, electronic mail (email),text message, multimedia and/or content data and so on. Non-limitingexamples of services provided comprise two-way or multi-way calls, datacommunication or multimedia services and access to a data networksystem, such as the Internet.

In a wireless communication system at least a part of a communicationsession between at least two stations occurs over a wireless link.

A user can access the communication system by means of an appropriatecommunication device or terminal. A communication device of a user isoften referred to as user equipment (UE) or user device. A communicationdevice is provided with an appropriate signal receiving and transmittingapparatus for enabling communications, for example enabling access to acommunication network or communications directly with other users. Thecommunication device may access a carrier provided by a station oraccess point, and transmit and/or receive communications on the carrier.

The communication system and associated devices typically operate inaccordance with a given standard or specification which sets out whatthe various entities associated with the system are permitted to do andhow that should be achieved. Communication protocols and/or parameterswhich shall be used for the connection are also typically defined. Oneexample of a communications system is UTRAN (3G radio). An example ofattempts to solve the problems associated with the increased demands forcapacity is an architecture that is known as the long-term evolution(LTE) of the Universal Mobile Telecommunications System (UMTS)radio-access technology. Another example communication system is socalled 5G radio access technology.

Where beam forming is used for communication between an access point anda user equipment, the amount of system overhead relating to training,beam tracking and beam switching may be relatively high.

SUMMARY

According to an aspect, there is provided a method comprising:transmitting beam cluster information to a user equipment, the beamcluster information defining a plurality of beam clusters and beamidentification information for each of a plurality of beams in arespective beam cluster of the plurality of beam clusters; andtransmitting, to the user equipment, at least one beam based on the beamcluster information.

According to an aspect there is provided a method comprising: receivingbeam cluster information from a beam forming access point, said beamcluster information defining a plurality of beam clusters, said beamcluster information defining beam identification information for each ofa plurality of beams in a respective beam cluster; and using said beamcluster information to control the processing of at least one beamreceived from said access point.

The method may comprise determining receive processing informationassociated with at least one beam received from said access point tocontrol receive processing of another beam of a beam cluster to whichthe at least one beam belongs.

This may control the initial receive processing.

Each cluster of beams transmitted by said access point may be associatedwith a set of antenna ports, wherein said receive processing informationcomprises respective antenna port information.

The determining said receive processing information may comprisetraining a receiving beamformer.

The method may comprise receiving a plurality of replicas of one or morebeams of a cluster, and using said plurality of replicas to train saidbeamformer.

The method may comprise receiving a plurality of reference beams fromsaid access point.

Each reference beam may comprise beam identity information.

The plurality of reference beams may be received in one or more sweepblocks.

The cluster information may comprise one or more of: clustered downlinkbeams; association to a set of one or more antenna ports; cluster size;periodicity of cluster; information associated with a next availablesubframe.

The method may comprise receiving said cluster information in abroadcast channel.

The method may comprise receiving said cluster information in a systeminformation block.

The method may comprise receiving said cluster information one ofperiodically or aperiodically.

The beam clusters may be configured dynamically or semi-statically.

The method may comprise receiving beam map information from said accesspoint for beams provided by said access point.

The beam map information may comprise a codebook definition.

The method may comprise sending a request to said access point, saidrequest requesting activation of one or more beams.

The request to said access point may be determined in dependence on beamcluster information and said beam map information.

A first beam may be received on one symbol of a subframe and at leastone other beam of said cluster may be received on a different symbol ofsaid subframe.

The method may be performed by an apparatus. The apparatus may beprovided in a communication device.

According to an aspect, there is provided a method comprising: receivinga first beam from a beam forming access point; determining receiveprocessing information for said first beam and to which of a pluralityof beam clusters said first beam belongs; and using said receiveprocessing information to control receive processing of another beam ofthe beam cluster to which the first beam belongs.

The method may be performed by an apparatus. The apparatus may beprovided in a communication device.

According to another aspect there is provided an apparatus comprising:means for receiving beam cluster information from a beam forming accesspoint, said beam cluster information defining a plurality of beamclusters, said beam cluster information defining beam identificationinformation for each of a plurality of beams in a respective beamcluster; and means for using said beam cluster information to controlthe processing of at least one beam received from said access point.

The method may comprise means for determining receive processinginformation associated with at least one beam received from said accesspoint to control receive processing of another beam of a beam cluster towhich the at least one beam belongs.

This may control the initial receive processing.

Each cluster of beams transmitted by said access point may be associatedwith a set of antenna ports, wherein said receive processing informationcomprises respective antenna port information.

The means for determining said receive processing information may be fortraining a receiving beamformer.

The receiving means may be for receiving a plurality of replicas of oneor more beams of a cluster, and using said plurality of replicas totrain said beamformer.

The receiving means may be for receiving a plurality of reference beamsfrom said access point.

Each reference beam may comprise beam identity information.

The plurality of reference beams may be received in one or more sweepblocks.

The cluster information may comprise one or more of: clustered downlinkbeams; association to a set of one or more antenna ports; cluster size;periodicity of cluster; information associated with a next availablesubframe.

The receiving means may be for receiving said cluster information in abroadcast channel.

The receiving means may be for receiving said cluster information in asystem information block.

The receiving means may be for receiving said cluster information one ofperiodically or aperiodically.

The beam clusters may be configured dynamically or semi-statically.

The receiving means may be for receiving beam map information from saidaccess point for beams provided by said access point.

The beam map information may comprise a codebook definition.

The apparatus may comprise means for sending a request to said accesspoint, said request requesting activation of one or more beams.

The apparatus may comprise means for determining said request to saidaccess point in dependence on beam cluster information and said beam mapinformation.

A first beam may be received on one symbol of a subframe and at leastone other beam of said cluster may be received on a different symbol ofsaid subframe.

The apparatus may be provided in a communication device.

According to another aspect, there is provided an apparatus comprising:means for receiving a first beam from a beam forming access point; meansfor determining receive processing information for said first beam andto which of a plurality of beam clusters said first beam belongs; andmeans for using said receive processing information to control receiveprocessing of another beam of the beam cluster to which the first beambelongs.

The apparatus may be provided in a communication device.

According to another aspect, there is provided an apparatus comprisingat least one processor, and at least one memory including computerprogram code, the at least one memory and the computer program codeconfigured to, with the at least one processor, cause the apparatus atleast to: receive beam cluster information from a beam forming accesspoint, said beam cluster information defining a plurality of beamclusters, said beam cluster information defining beam identificationinformation for each of a plurality of beams in a respective beamcluster; and use said beam cluster information to control the processingof at least one beam received from said access point.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause determining of receiveprocessing information associated with at least one beam received fromsaid access point to control receive processing of another beam of abeam cluster to which the at least one beam belongs.

This may control the initial receive processing.

Each cluster of beams transmitted by said access point may be associatedwith a set of antenna ports, wherein said receive processing informationcomprises respective antenna port information.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause the apparatus to train areceiving beamformer.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause the apparatus to receive aplurality of replicas of said first beam, and using said plurality ofreplicas to train said beamformer.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause the apparatus to receive aplurality of reference beams from said access point.

Each reference beam may comprise beam identity information.

The plurality of reference beams may be received in one or more sweepblocks.

The cluster information may comprise one or more of: clustered downlinkbeams; association to a set of one or more antenna ports; cluster size;periodicity of cluster; information associated with a next availablesubframe.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause the apparatus to receive saidcluster information in a broadcast channel.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause the apparatus to receive saidcluster information in a system information block.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause the apparatus to receive saidcluster information one of periodically or aperiodically.

The beam clusters may be configured dynamically or semi-statically.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause the apparatus to receive beammap information from said access point for beams provided by said accesspoint.

The beam map information may comprise a codebook definition.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause the apparatus to send arequest to said access point, said request requesting activation of oneor more beams.

The request to said access point may be determined in dependence on beamcluster information and said beam map information.

A first beam may be received on one symbol of a subframe and at leastone other beam of said cluster may be received on a different symbol ofsaid subframe.

The apparatus may be provided in a communication device.

According to another aspect, there is provided an apparatus comprisingat least one processor; and at least one memory including computerprogram code; the at least one memory and the computer program codeconfigured to, with the at least one processor, cause the apparatus atleast to: receive a first beam from a beam forming access point;determine receive processing information for said first beam and towhich of a plurality of beam clusters said first beam belongs; and usesaid receive processing information to control receive processing ofanother beam of the beam cluster to which the first beam belongs.

The apparatus may be provided in a communication device.

According to another aspect, there is provided a method comprising:causing beam cluster information to be transmitted from a beam formingaccess point, said beam cluster information defining a plurality of beamclusters, said beam cluster information defining beam identificationinformation for each of a plurality of beams in a respective beamcluster; and causing at least one beam to be transmitted from said beamforming access point with respective beam identification information.

The method may comprise causing a plurality of replicas of said one ormore beams of a cluster to be transmitted.

At least one beam may be caused to be transmitted in one or more sweepblocks.

The cluster information may comprise one or more of: clustered downlinkbeams; association to a set of one or more antenna ports; cluster size;periodicity of cluster; information associated with a next availablesubframe.

The method may comprise causing said cluster information to betransmitted in a broadcast channel.

The method may comprise causing beam map information to be transmittedfrom said access point for beams provided by said access point.

The beam map information may comprise a codebook definition.

The method may be performed by an apparatus. The apparatus may beprovided in an access point.

According to another aspect, there is provided an apparatus comprisingat least one processor, and at least one memory including computerprogram code, the at least one memory and the computer program codeconfigured to, with the at least one processor, cause the apparatus atleast to: cause beam cluster information to be transmitted from a beamforming access point, said beam cluster information defining a pluralityof beam clusters, said beam cluster information defining beamidentification information for each of a plurality of beams in arespective beam cluster; and cause at least one beam to be transmittedfrom said beam forming access point with respective beam identificationinformation.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause a plurality of replicas ofsaid one or more beams of a cluster to be transmitted.

At least one beam may be caused to be transmitted in one or more sweepblocks.

The cluster information may comprise one or more of: clustered downlinkbeams; association to a set of one or more antenna ports; cluster size;periodicity of cluster; information associated with a next availablesubframe.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause said cluster information tobe transmitted in a broadcast channel.

The at least one memory and the computer program code may be configuredto, with the at least one processor, cause beam map information to betransmitted from said access point for beams provided by said accesspoint.

The beam map information may comprise a codebook definition.

The apparatus may be provided in an access point such as a base station.

According to another aspect, there is provided an apparatus comprising:means for causing beam cluster information to be transmitted from a beamforming access point, said beam cluster information defining a pluralityof beam clusters, said beam cluster information defining beamidentification information for each of a plurality of beams in arespective beam cluster; and means for causing at least one beam to betransmitted from said beam forming access point with respective beamidentification information.

The apparatus may comprise means for causing a plurality of replicas ofsaid one or more beams of a cluster to be transmitted.

At least one beam may be caused to be transmitted in one or more sweepblocks.

The cluster information may comprise one or more of: clustered downlinkbeams; association to a set of one or more antenna ports; cluster size;periodicity of cluster; information associated with a next availablesubframe.

The apparatus may comprise means for causing said cluster information tobe transmitted in a broadcast channel.

The apparatus may comprise means for beam map information to betransmitted from said access point for beams provided by said accesspoint.

The beam map information may comprise a codebook definition.

Various causing means are provided in various embodiments. These causingmeans may be provided by the same and/or different means. The apparatusmay be provided in an access point such as a base station.

A computer program comprising program code means adapted to perform themethod(s) may also be provided. The computer program may be storedand/or otherwise embodied by means of a carrier medium. The computerprogram may be provided on a non transitory computer program carryingmedium.

In the above, many different embodiments have been described. It shouldbe appreciated that further embodiments may be provided by thecombination of any two or more of the embodiments described above.

Various other aspects and further embodiments are also described in thefollowing detailed description and in the attached claims.

BRIEF DESCRIPTION OF FIGURES

Embodiments will now be described, by way of example only, withreference to the accompanying Figures in which:

FIG. 1 shows a schematic diagram of a control apparatus according tosome embodiments;

FIG. 2 shows a schematic presentation of a possible communicationdevice;

FIG. 3 shows a schematic diagram of a sweeping sub-frame;

FIG. 4 shows a schematic diagram of a base station and three userequipment devices;

FIG. 5 shows a schematic diagram of an overview of frame structure;

FIG. 6 shows a schematic view of a base station beam arrangement in asweeping sub frame;

FIG. 7 shows a schematic view of a user device beamforming process fordifferent downlink beams;

FIG. 8 shows a schematic view of a beam map arrangement at atransmitter;

FIG. 9 shows a schematic view of beam group transmission;

FIG. 10 shows a schematic view of a beam clustering request;

FIG. 11 schematically shows an example of clustering informationleveraging at a receiver for its receiver beamformer training;

FIG. 12 shows a flowchart of an example method according to someembodiments; and

FIG. 13 shows a schematic view of a user device beamforming refinementprocess for different downlink beams.

DETAILED DESCRIPTION

In the following certain exemplifying embodiments are explained withreference to mobile communication devices capable of communication via awireless cellular system and mobile communication systems serving suchmobile communication devices. Before explaining in detail theexemplifying embodiments, certain general principles of a wirelesscommunication system, access systems thereof, and mobile communicationdevices are briefly explained with reference to FIGS. 1 to 2 to assistin understanding the technology underlying the described examples.

A communication device 10 or terminal can be provided wireless accessvia base stations or similar wireless transmitter and/or receiver nodesproviding access points of a radio access system.

Each of the access points may provide at least one antenna beam directedin the direction of the communication device 10 at a given time. In someembodiments a plurality of beams may be directed at a communicationdevice. The antenna beam can be provided by appropriate elements ofantenna arrays of the access points. For example, access links betweenthe access points (AP) and a user equipment (UE) can be provided byactive antenna arrays. Such arrays can dynamically form and steer narrowtransmission/reception beams and thus serve UEs and track theirpositions. This is known as user equipment-specific beamforming. Theactive antenna arrays can be used both at the access point and at theuser equipment device to further enhance the beamforming potential. Morethan one beam can be provided by each access point and/or antenna array.

Access points and hence communications there through are typicallycontrolled by at least one appropriate controller apparatus so as toenable operation thereof and management of mobile communication devicesin communication therewith. FIG. 1 shows an example of a controlapparatus for a node, for example to be integrated with, coupled toand/or otherwise for controlling any of the access points. The controlapparatus 30 can be arranged to provide control on communications viaantenna beams by the access points and on operations such as handoversbetween the access points. For this purpose the control apparatuscomprises at least one memory 31, at least one data processing unit 32,33 and an input/output interface 34. Via the interface the controlapparatus can be coupled to relevant other components of the accesspoint. The control apparatus can be configured to execute an appropriatesoftware code to provide the control functions. It shall be appreciatedthat similar components can be provided in a control apparatus providedelsewhere in the network system, for example in a core network entity.The control apparatus can be interconnected with other control entities.The control apparatus and functions may be distributed between severalcontrol units. In some embodiments, each base station can comprise acontrol apparatus. In alternative embodiments, two or more base stationsmay share a control apparatus.

Access points and associated controllers may communicate with each othervia fixed line connection and/or radio interface. The logical connectionbetween the base station nodes can be provided for example by an X2interface. This interface can be used for example for coordination ofoperation of the stations.

The communication device or user equipment (UE) 10 may comprise anysuitable device capable of at least receiving wireless communication ofdata. For example, the device can be handheld data processing deviceequipped with radio receiver, data processing and user interfaceapparatus. Non-limiting examples include a mobile station (MS) such as amobile phone or what is known as a ‘smart phone’, a portable computersuch as a laptop or a tablet computer provided with a wireless interfacecard or other wireless interface facility, personal data assistant (PDA)provided with wireless communication capabilities, or any combinationsof these or the like. Further examples include wearable wireless devicessuch as those integrated with watches or smart watches, eyewear,helmets, hats, clothing, ear pieces with wireless connectivity,jewellery and so on, universal serial bus (USB) sticks with wirelesscapabilities, modem data cards, machine type devices or any combinationsof these or the like.

FIG. 2 shows a schematic, partially sectioned view of a possiblecommunication device. More particularly, a handheld or otherwise mobilecommunication device (or user equipment UE) 10 is shown. A mobilecommunication device is provided with wireless communicationcapabilities and appropriate electronic control apparatus for enablingoperation thereof. Thus, the communication device 10 is shown beingprovided with at least one data processing entity 26, for example acentral processing unit and/or a core processor, at least one memory 28and other possible components such as additional processors 25 andmemories 29 for use in software and hardware aided execution of tasks itis designed to perform. The data processing, storage and other relevantcontrol apparatus can be provided on an appropriate circuit board 27and/or in chipsets. Data processing and memory functions provided by thecontrol apparatus of the communication device are configured to causecontrol and signalling operations in accordance with certain embodimentsas described later in this description. A user may control the operationof the communication device by means of a suitable user interface suchas touch sensitive display screen or pad 24 and/or a key pad, one ofmore actuator buttons 22, voice commands, combinations of these or thelike. A speaker and a microphone are also typically provided.Furthermore, a mobile communication device may comprise appropriateconnectors (either wired or wireless) to other devices and/or forconnecting external accessories, for example hands-free equipment,thereto.

The communication device may communicate wirelessly via appropriateapparatus for receiving and transmitting signals. FIG. 2 showsschematically a radio block 23 connected to the control apparatus of thedevice. The radio block can comprise a radio part and associated antennaarrangement. The antenna arrangement may be arranged internally orexternally to the communication device. The antenna arrangement maycomprise elements capable of beamforming operations.

Some embodiments relate to mobile communication networks withbeamforming techniques. For example, 5G radio access technology andLTE-A (Long term evolution—advanced) evolution have proposed usingbeamforming techniques. It should be appreciated that other embodimentsmay be used with any other communication system which uses beamforming.For example some wireless area networks may use beamforming.

The 5G radio system may use frequencies form 400 MHz to 100 GHz.Beamforming is considered to be desirable in enabling the use of thehigher frequency bands due to coverage issues. It should be appreciated,that other embodiments may use different frequency ranges.

Some transceivers (e.g. a hybrid transceiver architecture) may useanalogue beamforming, which may mean a large amount of narrow beams asthis is dependent on the number of antenna elements and carrierfrequency. It should be appreciated that other embodiments may be usedwith digital beamforming transceiver architecture or so-called hybridtransceiver architecture which use a hybrid of digital basebandprocessing (such as MIMO Multiple Input Multiple Output, and/or digitalprecoding) and analogue beamforming. It should be appreciated thatembodiments can be used with any method of beamforming.

Reference is made to FIG. 3 which shows an access points configured witha sweeping sub-frame The access point is shown changing the beams intime, at a first point in time it is denoted as 1 a, at a second pointin time as 1 a′ and at a third point in time as 1 a″. The access pointmay be a base station. In some standards, such as 5G, the access pointmay be referred to as a BS (Base station). A cell coverage area iscovered by beams transmitted by the access node. In the example shown inFIG. 3, six beams are shown for the access point. These are beam 1, beam2, beam 3, beam 4, beam 5, and beam 6. At each time instance, the accesspoint has two active beams in a sweeping block (SB) Consecutive sweepingblocks are transmitted by the base station, each sweeping blockconsisting of different beams compared to other sweeping blocks. Beam 1and beam 2 are active at first time instance in the sweeping block 1,beam 3 and beam 4 are active for the second sweeping block 2, and beamSand beam 6 are active for the Nth sweeping block N. During a sweepingblock, only some of the beams are active, the rest of the beams areinactive. It should be appreciated that in different embodiments, moreor less than six beams may be provided.

There are N sweeping blocks where N is an integer. There may be M beamsper block where M is an integer. M and/or N may in some embodiments be 2or more.

In some embodiments the number of active and inactive beams provided mayalso vary over time. The number of active beams may vary between theaccess points.

To enable system access, periodical transmission of system informationmay be required per direction where one or more beams cover a specificarea of a cell. The corresponding directions may need to be covered toprovide resources for system access. When an access point covers aspecific area with a set of beams during a time interval (such as symbolduration or two symbol durations) it is called a sweep block. FIG. 3illustrates the concept of sweep blocks. For sweep block SB #2 the beams3 and 4 are active and for sweep block SB #N the beams 5 and 6 areactive. Although FIG. 3 illustrates that adjacent beams are activeduring sweep block it should be understood that a different set of beamsmay be selected for a given sweep block. Active beams are referenced Ain FIG. 3 and inactive beams are referenced I.

FIG. 3 further depicts a sweeping sub-frame SSF. The sweeping sub-framemay provide coverage for common control channel signaling withbeamforming. The sweeping sub-frame consists of sweeping blocks SB.

The total number of beams required to cover the required cell area maybe larger than the number of concurrent active beams that the accesspoint is able to form. Therefore access points need to sweep through thecell coverage area in the time domain by activating a different set ofbeams on each sweep block. Depending on the number of active beams persweep block and on the total number of beams required to cover a cellarea, two or more sweep blocks may be required. Furthermore, the numberof sweep blocks per sub-frame is limited by the length of each sweep. Asan example, one sweep block duration may be one or two symbols (forexample, OFDM (orthogonal frequency-division multiplexing) symbols) andif there are 14 symbols per sub-frame, the sweeping sub-frame would beable to accommodate 7 or 14 sweep blocks. Depending on the number ofsweep blocks required to cover a cell, a plurality of sweepingsub-frames may be needed. However, this is by way of example only anddifferent configurations may be used in different embodiments.

The active beams depicted in FIG. 3 may be used for either transmittingor receiving information. The sweeping sub-frame can therefore bedefined as a downlink sweeping sub-frame, when the active beam istransmitting information, or as an uplink sweeping sub-frame, when theactive beam is receiving information. Furthermore, assuming a TDD (timedivision duplex) system and reciprocity between downlink and uplinkchannels, to cover a cell area on the uplink and the downlink directionswith the same beam configurations per sweep block, the same sweep blocksneed to be defined on uplink and downlink direction.

As an example of downlink direction, if downlink common control channelcoverage is provided by the sweeping sub-frame, each sweep block maycarry cell access information such as one or more of downlinksynchronization signals, system information such as MIB (masterinformation block), SIB (system information block) or the like. Otherexamples or information which may be include alternatively oradditionally comprise one or more of, PRACH/RACH (physical random accesschannel and random access channel configurations), paging, and anycontrol information that needs to be broadcasted in a cell. In theuplink direction, the sweeping sub-frame/sub-frames may accommodateresources for the random access channel or other uplink channelsrequiring periodic availability such as SR (scheduling request).

A non-limiting definition for a beam is a detection of a beam specificreference signal (BRS). In one example, a beam specific reference signalBRS is mapped to an antenna port which maps to at least one, typically aplurality of, antenna elements. The signals leading to the antennaelements are individually weighted (depending on architecture this maybe analogue or digital weighting), to form a specific radiation pattern.

Multiple antenna ports may be defined (thus multiple radiation patternsmay be formed) which are identified by detection of different beamspecific reference signals. These radiation patterns may be equallyshaped but may point in different directions.

A single beam specific reference signal may be mapped to two or moreantenna ports which may or may not map to the same antenna elements. Insome embodiments, antenna elements can be mapped dynamically todifferent ports. One example is to transmit a beam specific referencesignal using two antenna ports where the antenna element specificweights are equal, but the first antenna port maps to elements that arehorizontally polarized (H-polarization) and second antenna port maps toelements which are vertically polarized (V-polarization). Thus, theradiation patterns of the elements of the first and second ports are thesame but as same beam specific reference signal is transmitted throughboth ports they are observed as a single beam. In some embodiments, abeam specific reference signal may be transmitted on two or more portswhere the antenna element specific weighting is not equal (differentradiation patterns).

In a beamformed system where the cell coverage is provided by multiplebeams, it may be beneficial to identify a single beam e.g. by using beamspecific reference signals enabling user equipment to perform beam leveldetection/separation and perform measurements on beam specific referencesignal. The measurements may determine indicators such as, but limitedto, one or more of Reference Signal Received Power (RSRP), ReferenceSignal Received Quality (RSRQ), received signal strength indicator(RSSI)), channel quality indicator (CQI) or the like. Identifyingdifferent beams may be beneficial e.g. when user equipment indicates tothe network access point the preferred communication beam during initialaccess or mapping a measurement to a common reference index whenreporting the measurements to the network access point.

To identify a beam, the following mappings can be made: e.g. if eightdifferent beam reference signals are transmitted per sweep block, thereceiver is potentially able to measure eight different signal indices(beams or beam indices). The eight different BRS signals arecorresponding to eight antenna ports. The same beam specific referencesignal antenna ports may be reused in the next sweep block, thus thesweep block ID may need to be determined to be able to determine thebeam index. Thus, the beam index may be calculated by:

Beam index=BRS antenna port*Sweep block index.

The sweep block index may be explicitly signalled if the sweep block(sweep symbol or multiple symbols) convey also one or more ofinformation such as MIB, SIB, DL CTRL (downlink control), DL DATA(downlink data) and/or the like. Alternatively or additionally, thesweep block may include a specific sequence number to identify theblock.

To achieve sufficient coverage and capacity in a cellular network,propagation/path loss of the radio channel at high carrier frequencies,e.g. 28 GHz or similar frequencies, may be compensated by introducingdirective transmission and reception in the form of beamforming, e.g.via large scale antenna arrays. As a result of this, relatively largeantenna array gains, at both the access point, (e.g. 18 dB with 64antenna elements) and the user equipment (e.g. 9 dB with 8 antennaelements) may be achieved to compensate propagation loss and/or lossesfor example due to rain and oxygen absorption. Different embodiments mayof course operate at different carrier frequencies.

Some embodiments may use a carrier frequency of 28 GHz and a systembandwidth of 100 MHz. However, this is by way of example only anddifferent carrier frequencies and/or bandwidths may be used in otherembodiments.

Some embodiments may use a hybrid multi antenna deployment at the basestation (BS). The UE may be able to perform analog/RF beamforming or anyother suitable beamforming. Some embodiments may provide a signallingmethod to enable beam transmission and exploitation at the receiver.

To exploit the full merit of large scale antenna arrays, such as phasedantenna array technology, directivity at transmitter and receiver needto be dynamically adjusted according to a deployment scenario andpotential changes in a radio link between transmitter and receiver. Inpractice, especially in cellular networks with multiple access pointsand users, this may lead to excessive amount of system overheads relatedto beamformer training, beam tracking and beam switching at the userequipment and associated signalling needs between access point and userequipment (e.g. a beam report providing beam specific reference signalmeasurements or carrying CSI (channel state information).

Reference is made to FIG. 4 which illustrates that both user equipmentand network (access point) beamforming may be used. FIG. 4 shows anaccess point 40, and three user equipment devices UE1, UE2, UE3. Theaccess point beams, 41-47, and user equipment beams 50-56 of UE1, UE2and UE3 are also schematically illustrated. Each user equipment is shownto have a different receiving beam resolutions Rx by way of example.

As described above, access point coverage is provided by forming a setof beams that cover a part of the cell area, thus the user equipment maydetect a plurality of beams as the radiation patterns of different beamstypically overlap to provide solid coverage (FIG. 4 illustrates asimplified view).

Depending on the user equipment's communication beam direction, adifferent beam, or set of beams may be detected. In addition to this,the case of an omnidirectional beam should also be discussed. As anarrow beam illustrates higher antenna gain (obtained by using aplurality of elements, weighted accordingly to point the main lobe), theomnidirectional beam has equal antenna gain to all directions. Thus, theuser equipment is able to detect signals from all directions (alsointerference) but with lower antenna gain.

UE1 operates with four receiving beams 50-54 and matches receiving beam52 with the access point transmitting beam 43, as illustrated by meansof matching shading in FIG. 4.

UE2 is an omnidirectional user equipment for which the best downlinkbeam is access point beam 44.

UE3 is operating only two receiving beams, 55, 56, and matches beam 56with the access point beam 45.

In some embodiments, to enable a communication device to performefficient and relatively low complexity beamformer training for areceiver and/or transmitter, a network access point may provideassistance information on the characteristics of transmitted downlinkbeams as a part of a periodic downlink broadcasting subframe. Thisassistance information is cluster information.

Dynamic/semi-static signalling of clustering information may be providedin some embodiments.

This cluster information may be defined by the access point and/or byone or more network apparatus.

The clusters may be defined in any suitable manner. In some embodiments,regular patterns of clusters may be defined. In some embodiments, allthe clusters may be of the same size. In some embodiments, differentclusters may have different numbers of beams. The cluster shape may beregular or irregular.

In examples described later various different shapes and sizes ofcluster are illustrated. For example, in FIG. 7, beams 1, 3, 7 are acluster. FIG. 9 shows another example of clusters.

In some embodiments, the radio environment may be taken into accountwhen defining the cluster size and/or shape and/or position.

Any suitable criteria may be used for defining the position and numberof cluster beams. For example, one criteria may be spatial correlationbetween beams. This correlation could be higher or lower. Alternativelyor additionally, spatial “proximity” may be taken into account. Forexample, neighbour beams may be in a cluster even if they are not highlycorrelated from a signal processing point of view.

The number of beams in a cluster may be preconfigured.

In some embodiments, the number of beams in a cluster may be dependenton the beam width. For example, for wider beams there may be fewer beamsin a cluster as compared to narrower beams. By way of example only, ifthere are wide beams in the cell, then there might be a low number ofbeams in cluster, e.g. 3. If there are narrow beams in the cell, theremay be more beams in the cluster, e.g. 5.

The clusters are defined by the access point. According, the cluster orclusters used by a user device will depend on its position in the cell.Two UEs next to each other might experience beams from same cluster.

In some embodiments, information about the all of the clustersassociated with an access point are provided to a UE. In otherembodiments, information about only a subset of the clusters areprovided to a UE.

In some embodiments, the clustering information of a set of downlinktransmit TX beams is associated with a set of antenna ports to bedecodable/detectable by a communication device.

The clustered antenna ports may be provided in a downlink broadcastingsweeping subframe(s) (BRS—beam reference signal).

The clustered antenna ports may be are periodically or a periodicallytransmitted to a particular UE (BRRS—beam refinement reference signal).

DL beam clustering information may define spatial characteristics ofdownlink beams of broadcast sweep subframe distributed over singleand/or a plurality of sweep subframes.

Clustering information may comprise one or more of: clustered downlinkbeams and their association to a set of antenna ports, cluster size, andperiodicity of a cluster at symbol and/or subframe and/or radio framelevel.

Clustering information may be provided explicitly into a master systeminformation block MSIB and/or a secondary system information block SSIB.

Clustering information may alternatively or additionally be obtainedimplicitly from a symbol(s) in a sweeping subframe. The may be providedas a combination of one or more information from synchronizationsignals, initialization of sequences, and information from a broadcastchannel.

Clustering information may be captured by a beam cluster index.

In one embodiment, a UE is informed of a beam map consisting of a fulldownlink beam arrangement in the DL.

In some embodiments, assistance information on the clustering ofdownlink TX beams associated with a set of TX antenna ports may be usedat the communication device for its TX/RX beamformer training and/orrelated measurements at the communications device.

In some embodiments by leveraging beam clustering assistanceinformation, RX beamformer weights, e.g. phase and/or amplitude, can betrained. This may improve reliability and/or reduce computationalcomplexity.

By exploiting the clustering information provided by a network accesspoint, a communication device can generate clustering of DL beams anduse generated clustering for its RX and/or TX beamformer training.

In some embodiments, a communications device is able to trigger thetransmission of reference signals RS on beams which were not active in aprevious transmission.

Some embodiments may provide network assistance information for acommunication device via broadcasting sweep subframe ordynamic/semi-static signalling to enhance the capability of thecommunication device to train its RX beamformer. By using assistanceinformation, the communication device can have a priori informationabout the clustering of downlink beams. Therefore, the communicationdevice may be able to perform more reliable and efficient training of aRX beamformer with respect to a situation without any a prioriinformation.

Reference is made to FIG. 6 which shows a base station beam arrangementin the sweeping subframe. Different circle line types (continuous, dash,dot) are used to indicate beams which are transmitted in the same OFDMsymbol. In the example of FIG. 6, beams #1, 2, 3, 4, 5, 6 aretransmitted in one OFDM symbol, beams #7, 8, 9, 10, 11, 12 aretransmitted in a different OFDM symbol, beams #13, 14, 15, 16, 17 aretransmitted in yet another OFDM symbol. It can be seen that in one OFDMsymbol the UE covers both azimuth and elevation dimensions. Beamclustering information would indicate to the UE beam neighbours forwhich the UE could utilize same (or close) receiver processing.

Reference is made to FIG. 7 which illustrates some example beamclustering. FIG. 7 shows a UE beamforming process for different DLbeams. For example, in FIG. 7, beams #1, 7, 3 can be signalled as partof one spatial cluster which is referenced 700. This is associated witha first Rx filter #1. Beams #3, 5, 16 can be signalled as part ofanother spatial cluster which is referenced 702. This is associated witha Rx filter referenced #4. Beams #9, 13, and 15 can be signalled as partof another spatial cluster which is referenced 701. This is associatedwith a Rx filter referenced #2.

The UE could utilize same Rx beamforming processing, for a givencluster. The beams part of an indicated cluster can be regarded ashaving a spatial diversity smaller compared to beams not part of anindicated cluster. Take beams #1, 8 and 17 which are far apart, thesebeams would have a larger spatial diversity than the beams in anycluster. For different beam clusters the UE may use different Rxprocessing. This cluster information may assist in UE processing asfollows: when the UE is processing beam #1, the UE derives UEbeamforming Rx-1. Having the beam clustering information, when the UE isprocessing at a later stage beams from the same cluster but in differentsymbols, such as beam #7 or #3, the UE knows that Rx-1 is a firstcluster to consider.

However, as shown in FIG. 7 alternative receiver assumptions need to beconsidered by the UE, for example beam #3 may be processed with UEbeamforming filter Rx #1 associated with the first cluster 700 or thefilter Rx-#4 associated with the cluster referenced 702, the UE wouldfilter Rx #1 associated with the first cluster 700 as first alternative.Beam #3 can be also processed by the filter associated with the groupreferenced 702.

In FIG. 7, beams 1, 2, 3 . . . 6 are transmitted in first sweepingblock. When UE is detecting beam #1 it is using a UE receiver Rx number1. For each beam, the UE needs to test its receiver beams—this can beRx1, Rx2, . . . Rx 4 or up to RxN for example, hence the UE also does aform of beam sweeping on its Rx beams. After detecting beam #1 the UEmoves to beam #2 where a different Rx receiver is used. However, whenthe UE moves to beam #3, it knows that it is part of cluster 700, andthe UE also knows that for beam 1 it used Rx1, hence the beams in acluster are likely to need the same Rx receiver at the UE. Knowing thecluster helps in that the UE does not need to test all of its Rx beams.

For a particular beam the UE is sweeping its Rx beams and for each Rxbeams is computing a metric, for example RSRP. The Rx beams which givethe highest RSRP is declared the “winner”.

Reference is made to FIG. 8 which shows, as an example, all possiblebeams which can be formed at the transmitter. This provides a “beammap”. By creating clusters of beams and indicating this to the UE, theUE is able to recreate the beam map. In some embodiments, this may allowthe UE to recreate the map even if not all the beams are transmittedand/or active in the downlink. It should be noted that the beamnumbering used in FIG. 8 is different to that of FIGS. 6 and 7.

A beam map may be indicated to the UE by signalling the number ofhorizontal beam rows, the number of vertical beam columns, the shift inbeam index between two adjacent beams on same row, if different amountof beams are in the odd and even rows. For example, in the case of theembodiment shown in FIG. 8, if the first beam index is 1, then the nextis 13, so the BS signals have a modulo 12 as difference between twobeams indices where the beams are adjacent in a given row. Thus, in someembodiments, a definition may be provided to the UE which allows the UEto determine the map with the beam indices. In other embodiments, theinformation providing the beam map may take any suitable form. Forexample, a “bit map” representation may be used to define the locationof beam indices in a beam index map.

FIG. 9 shows the transmission of clusters of active beams. This may beperformed in a UE specific manner. The indication of the clusters may beprovided by dynamic or semi-static signalling. A first beam clustershown in FIG. 9 is formed by beams #13, 25, 27, 39, 4, 6, 18. A secondcluster is formed by beams #28, 40, 7, a third adjacent cluster isformed by beams #21, 33, 35, 47, a fourth cluster is formed by beams#38, 3, 15, 17, 29 and a fifth cluster is formed by beams #10, 22, 36and 48. Such clusters can be enabled by means of a downlink beamspecific RS such as a beam refinement RS, by signalling beam clusterinformation via a sweep subframe or in any other suitable manner.

As discussed previously, the UE is provided with information such thatthe UE has or is able to recreate the beam map shown in FIG. 8. If thetransmitted beams are not sufficient, the UE could cause the triggeringof the beams which are not active for that UE, hence in order to operateefficiently in the presence of mobility. This may be done by the UEsending a request or a trigger to the base station to cause these beamor beams to be activated for the UE.

For example in FIG. 10, the beams #30, 44, 9 are shown in dashed lineswhich can be requested/triggered by the UE (these beams have not beenactive at a previous time, as shown in FIG. 9). This is possible as theUE knows the beam map.

By exploiting the reciprocity of channel, DL TX beams can be used asuplink RX beams at base station and DL RX beams at UE can be used as TXfor uplink.

Some embodiments may minimize/avoid the usage of dedicated referencesignal, e.g. BRRS, for beam training, tracking and switching purposes.As a result, the efficiency of a wireless systems, in terms of overheadand latency, may be improved.

Periodic clustering information of a set of downlink beams may beassociated with a set of reference signal antenna ports e.g. BRS. Theclustering information may be encoded explicitly as a part of broadcastchannel, e.g. PBCH (physical broadcast channel) and/or SIB (systeminformation block). These channels may be respectively referred to asxPBCH and xSIB in the proposed 5G system.

The periodic clustering information may include one or more of thefollowing: antenna port specific clustering periodicity at subframeand/or symbol level; and the size of cluster per each antenna portassociated with the set of antenna ports.

Aperiodic clustering information of downlink beams may be associatedwith a set of reference signal antenna ports e.g. BRS. Aperiodicclustering information may be encoded explicitly as a part of broadcastchannel, e.g. PBCH (physical broadcast channel) and/or SIB (systeminformation block). These channels may be respectively referred to asxPBCH and xSIB in the proposed 5G system. The aperiodic clusteringinformation may include one or more of the following: next availablesubframe number for each antenna port associated with the set of antennaports; and symbol number associated with next available subframe.

In some embodiments, a set of indices to a beam cluster codebook or beammap codebook may be encoded as a part of the broadcast channel, e.g.PBCH (physical broadcast channel) and/or SIB (system information block).The encoding may be explicit or implicit.

The cluster codebook may define a plurality of options for beamclustering or beam map. A beam cluster may have one or more of a sweepsubframe duration; number of antenna ports, granularity of spatialsampling in azimuth and/or elevation domains, clustering periodicity,and the size of a cluster. Different options may have one or more of:different sweep subframe durations; different numbers of antenna ports,different granularity of spatial sampling in azimuth and/or elevationdomains, different clustering periodicity, and different size of acluster.

A cluster codebook/beam map can be constructed in any suitable way. Forexample, the 3GPP standard has a 3GPP 2D-codebook definition (assumes 2DDFT (discrete Fourier transform) beams) where a number of antenna portsand oversampling factor per azimuth and elevation are defined and covera spanned 2D beam space.

By using a priori information (i.e. information known in advance) ofclustered TX beams a communication device is enabled to have a pluralityof copies/replicas of a transmitted signal arriving from nearly samedirections associated with a cluster. As a result of this, a receiverhas the opportunity to train/adjust its beamformer weights, e.g.amplitude and/phase to correspond intended direction.

In this regard, reference is made to FIG. 13. The BS sends a small burstof BRRS for each replica in the burst, and the UE is fine tuning itsreceiver. Replicas of the Rx beam are depicted by the overlappingcircles, the beams associated with each of groups 700, 701 and 702 beingillustrated. As can be seen, there are more replicas for each of thegroups than the three beam of the group. The UE is trained by thereception of the replicas during the BRRS burst. Reference 704 shows therefinement resolution between the replica beams. On each successivereplica, the UE is able to orient its beams better and better towards aparticular direction.

Periodic clustering information of downlink beams may be associated witha set of reference signal antenna ports e.g. BRS.

The clustering information may be implicitly encoded as a part of valuesand parameterization of other signals and channels within a sweepsubframe. This information may be antenna port specific clusteringperiodicity which may be at the subframe and/or symbol level and/or thesize of cluster per each antenna port associated with the set of antennaports.

Periodic/aperiodic clustering information of downlink beams may beassociated with a set of UE specific reference symbols, e.g. BRRS.

The clustering information may be signalled dynamically orsemi-statically.

The UE may be able to trigger beams which are not active, based on thereference symbols map and clustering information.

FIG. 5 shows an example of DL beam cluster information association witha downlink broadcasting sweep subframe. In this particular example, beamclusters have the periodicity of four OFDM symbols in the first twosubframes. With reference to FIG. 5, there is shown an overview of theframe structure and the positions of relevant downlink and uplinksignals and channels. Each frame has a DL sweeping sub-frame 116 with 14OFDM symbols; SSS (secondary synchronisation signal), PSS (primarysynchronisation signal), ESS (enhanced system selection) BRS, PBCH(physical broadcast channel) being provided in each symbol. The downlinktransmission beams DL TX are associated with RS reference signal, forexample the BRS, antenna ports from which the RSRP or similarmeasurements for P different beam groups are computed.

FIG. 5 shows a first DL sweep frame 116 a and the next DL sweep frame116 b. By way of example, symbols 0, 4, 8 and 12 are highlighted in onesub-frame and symbols 1, 5, 9 and 13 in the next. This shows how acluster may have periodicity, e.g. every 4th symbol within a sub-frame(116 a and 116 b). This is by way of example only and in someembodiments the periodicity may be the same or different.

This is followed by a UL sweeping sub-frame 104. This is followed by aDL/UL sub-frame 120. This has a first field 106 for DL CTRL information,a second field 108 for DMRS information, and 11 fields 112 for UL data,DL data and CSI-RS/SRS (sound reference signal). The last field 110 isfor UL CTRL information. Based on RSRP or similar measurements, the UEsends a periodic or aperiodic single joint beam group report covering Pdifferent groups or separately P different beam group reports via ULcontrol. The frame may have a 5 ms periodicity.

FIG. 11 shows an example how clustering information with four TX beamscan be leveraged at a receiver with two beams. As can be seen, by usingclustering information a receiver is enabled to observe multiple copiesof transmitted signal arriving nearly from the same direction to thereceiver. As a result of this, the receiver has an improved chance totrain/adjust its beamformer weights to correspond to intendeddirections. This Figure shows an example of beam clustered assistedtraining in sub-frame 1 (SF1). There are 4 TX beam clusters, wheredifferent clusters are formed as follows: cluster 1 (with beamsreferenced 920, 924, 928, 932), cluster 2 (with beams referenced 921,925, 929, 939), cluster 3 (with beams referenced 922, 926, 930, 934) andcluster 4 (with beams referenced 923, 927, 931, 935). A first beam ofeach cluster is in symbol S0, a second beam of each cluster is in symbolS4, a third beam of each cluster is in symbol S8, a fourth beam of eachcluster is in symbol S12. At RX side, there are 2 RX beams available atthe time. Now, UE has received e.g. via the PBCH clustering information,e.g. number of cluster, cluster size, cluster periodicity, antenna portassociation per cluster. Based on this information, UE is aware of atwhich symbols beams are belonging to certain clusters. Hence, the UE canleverage this information when it is performing its RX beamformer weighttraining. For example, at symbol 0 UE achieves with its RX beams 901 and902 maximum RSRP values. Therefore, by using clustering information, theUE knows at symbols 4, 8, 12 it can use again “more less the same” RXbeams as e.g. for the first symbol S0. Therefore, the UE may save a lotof its computational complexity as well latency associated with trainingby using clustering information. Thus, the beams 903 and 904 used forsymbol S4 are similar or the same as used for symbol S0. Similarly forthe beams 905 and 906 for symbol S8 and beams 901 and 904 for symbolS12.

Embodiments may be used in co-located and/or non co-located antennadeployments.

With reference to FIG. 12, there is shown an example of a methodaccording to an embodiment.

In step S1, cluster information is received from the access point. Thecluster information may be as discussed previously. It should beappreciated that in other embodiments, the UE may otherwise obtain thecluster information.

In step S2, the UE may receive a reference beam or other beam from theaccess point. This may be received in a sweep block such as discussedpreviously.

In step S3, the UE may determine receive processing information, forexample a receive filter and/or other receive processing information.The UE may determine which cluster or clusters the received beam isassociated.

In step S4, the UE may use the same or similar receive processinginformation when receiving another beam of the same cluster at leastinitially to see if that receive processing information is alsoappropriate for that other beam of the same cluster.

The required data processing apparatus and functions may be provided bymeans of one or more data processors. The apparatus may be provided inthe communications device, in the control apparatus and/or in the accesspoint. The described functions at each end may be provided by separateprocessors or by an integrated processor. The data processors may be ofany type suitable to the local technical environment, and may includeone or more of general purpose computers, special purpose computers,microprocessors, digital signal processors (DSPs), application specificintegrated circuits (ASIC), gate level circuits and processors based onmulti core processor architecture, as non-limiting examples. The dataprocessing may be distributed across several data processing modules. Adata processor may be provided by means of, for example, at least onechip. Appropriate memory capacity can also be provided in the relevantdevices. The memory or memories may be of any type suitable to the localtechnical environment and may be implemented using any suitable datastorage technology, such as semiconductor based memory devices, magneticmemory devices and systems, optical memory devices and systems, fixedmemory and removable memory.

In general, the various embodiments may be implemented in hardware orspecial purpose circuits, software, logic or any combination thereof.Some aspects may be implemented in hardware, while other aspects may beimplemented in firmware or software which may be executed by acontroller, microprocessor or other computing device, althoughembodiments are not limited thereto. While various aspects may beillustrated and described as block diagrams, flow charts, or using someother pictorial representation, it is well understood that these blocks,apparatus, systems, techniques or methods described herein may beimplemented in, as non-limiting examples, hardware, software, firmware,special purpose circuits or logic, general purpose hardware orcontroller or other computing devices, or some combination thereof. Thesoftware may be stored on such physical media as memory chips, or memoryblocks implemented within the processor, magnetic media such as harddisk or floppy disks, and optical media such as for example DVD and thedata variants thereof, CD.

The foregoing description has provided by way of exemplary andnon-limiting examples a full and informative description of exemplaryembodiments. However, various modifications and adaptations may becomeapparent to those skilled in the relevant arts in view of the foregoingdescription, when read in conjunction with the accompanying drawings andthe appended claims. However, all such and similar modifications of theteachings of this description will still fall within the spirit andscope of embodiments as defined in the appended claims. Indeed there isa further embodiment comprising a combination of one or more of any ofthe other embodiments previously discussed.

1. A method comprising: transmitting beam cluster information to a userequipment, the beam cluster information defining a plurality of beamclusters and beam identification information for each of a plurality ofbeams in a respective beam cluster of the plurality of beam clusters;and transmitting, to the user equipment, at least one beam based on thebeam cluster information.
 2. The method as claimed in claim 1, whereinthe beam cluster information is associated with a set of antenna ports.3. The method as claimed in claim 1, wherein the beam clusterinformation indicates to the user equipment beam neighbors for which theuser equipment utilizes a receiver filter.
 4. The method as claimed inclaim 1, further comprising transmitting a plurality of replicas of theat least one beam of corresponding beam cluster for training a receivingbeamformer.
 5. The method as claimed in claim 1, wherein the at leastone beams are associated with a set of antenna ports.
 6. The method asclaimed in claim 1, wherein each of the at least one beams comprisesbeam identity information.
 7. An apparatus comprising: at least oneprocessor; and at least one memory including computer program code; theat least one memory and the computer program code configured at leastto: transmit beam cluster information to a user equipment, the beamcluster information defining a plurality of beam clusters and beamidentification information for each of a plurality of beams in arespective beam cluster of the plurality of beam clusters; and transmit,to the user equipment, at least one beam based on the beam clusterinformation.
 8. The apparatus as claimed in claim 7, wherein the beamcluster information is associated with a set of antenna ports.
 9. Theapparatus as claimed in claim 7, wherein the beam cluster informationindicates to the user equipment beam neighbors for which the userequipment utilize a receiver filter.
 10. The apparatus as claimed inclaim 7, wherein at least one memory and the computer program code areconfigured to, with the at least one processor, further cause theapparatus to: transmit a plurality of replicas of the at least one beamof a corresponding bean cluster for training a receiving beamformer. 11.The apparatus as claimed in claim 7, wherein the at least one beams areassociated with a set of antenna ports.
 12. The apparatus as claimed inclaim 7, wherein each of the at least one beams comprises beam identityinformation.
 13. A non-transitory computer-readable storage mediumstoring instructions that when executed cause a processor to: transmitbeam cluster information to a user equipment, the beam clusterinformation defining a plurality of beam clusters and beamidentification information for each of a plurality of beams in arespective beam cluster of the plurality of beam clusters; and transmit,to the user equipment, at least one beam based on the beam clusterinformation.
 14. The non-transitory computer-readable storage medium asclaimed in claim 13, wherein the beam cluster information is associatedwith a set of antenna ports.
 15. The non-transitory computer-readablestorage medium as claimed in claim 13, wherein the beam clusterinformation indicates to the user equipment beam neighbors for which theuser equipment utilizes a receiver filter.
 16. The non-transitorycomputer-readable storage medium as claimed in claim 13, wherein theinstructions, when executed, further cause the processor to: transmit aplurality of replicas of the at least one beam of a corresponding beancluster for training a receiving beamformer.
 17. The non-transitorycomputer-readable storage medium as claimed in claim 13, wherein the atleast one beams are associated with a set of antenna ports.
 18. Thenon-transitory computer-readable storage medium as claimed in claim 13,wherein each of the at least one beams comprises beam identityinformation.